| High in-situ stress environment is the biggest feature of deep rock mass engineering,drilling and blasting is still the main method of deep hard rock excavation.The blasting excavation of deep rock mass is the result of the combined effect of dynamic stress and high in-situ stress produced by explosive explosion.The existence of in-situ stress changes the propagation direction and extension length of blast cracks,which affects the crushing effect and blasting efficiency of rock mass.The change of crack zone shape further affects the vibration characteristics of blasting seismic waves and the radiation pattern of seismic waves outside the crack zone.It is the basis of seismic wave prediction and safety protection for blasting excavation of high-stress rock mass to explore the cracking mechanism of rock mass,the composition of seismic wave and the attenuation law of seismic wave propagation.In this paper,a series of studies are carried out on the effects of in-situ stress on rock mass blasting cracking,seismic wave composition and propagation and attenuation law in the deep rock mass blasting excavation process by combining theoretical analysis,numerical calculation and engineering verification.The main research results are as follows:(1)Based on the basic theory of elastic dynamics,the stress field superposed by the explosion stress wave and the ground stress is studied by using Laplace transform method.On this basis,the rock blasting mechanism under high in-situ stress is analyzed.Due to the effect of in-situ stress,the radial and hoop compressive effects of the rock mass are strengthened,while the tensile effect is weakened;The in-situ stress mainly inhibits the rock mass in the middle and far zone of blasting,but has little effect on the rock mass in the near zone.crushed zone cracked zone(2)The SPH-FEM coupled numerical simulation method was used to study the effect of in-situ stress on the process of rock blasting cracking and the morphology of the blasting cracking zone(blast seismic wave generation zone).The results show that the in-situ stress has almost no effect on the range,shape and crack growth rate of the crushed zone,but it has a significant inhibitory effect on the tensile failure of the rock mass in the cracked zone.The higher the in-situ stress level,the smaller the fracture zone and crack propagation speed.Under non-hydrostatic in-situ stress field,cracks mainly propagate along the direction of the maximum principal stress,and finally the shape of the crack zone is elliptical.(3)The SPH-FEM coupled numerical simulation method was combined with the field measured data to analyze the influence of the morphological change of the blasting crack zone(blast seismic wave generation zone)on the energy of the explosion seismic wave under high in-situ stress conditions,and the propagation attenuation law of the explosion seismic wave under high in-situ stress.The research results show that the energy of the explosion seismic wave increases with the increase of the in-situ stress level,and the energy density of the seismic wave in the direction of the minimum principal stress is greater than that in the direction of the maximum principal stress;The SH wave is only generated in the non-hydrostatic in-situ stress field,and the peak of the SH wave in the direction of the minimum principal stress is greater than the peak of the SH wave in the direction of the maximum principal stress;As the level of in-situ stress increases,the micro-cracks in the rock mass will undergo a compression-closed-fracture state,the seismic wave energy attenuation rate will first decrease and then increase,and the attenuation rate of seismic wave energy in the direction of the minimum principal stress is lower than that in the direction of the maximum principal stress;The vibration monitoring speed in the surrounding rock and the surrounding rock surface during the blasting excavation of the Jinping Deep Underground Laboratory verified the reliability of the above analysis results. |
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